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About replacing individual LEDS on BL strips

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    #1

    About replacing individual LEDS on BL strips

    Hi There!
    Having fixed 5-6 TV sets by replacing full LED strips, and having watched other people fix that by replacing just one LED in the strip, my question now is what should I consider before doing so.

    At this time I have some old strips removed from TV's with all but one LED working. Are there different voltage/current LED on different strips? Are 99% of them just the same and interchangeable?

    How do you find which specific model is needed for each strip? When I check if a LED is OK by attaching the multimeter leads to the individual led pads on the strips I can see the LED lighting up very dim, due to the low voltage applied from the multimeter in DIODE TEST mode. Can I trust this level of brightness to compare to other LEDS in order to find a compatible replacement?

    Would you also just "jumper" an individual LED just to skip it? Maybe with an equivalent resistor?

    Thanks a lot!
    Last edited by edugimeno; 11-07-2022, 12:03 PM.
    Tags: None
    #2
    Re: About replacing individual LEDS on BL strips

    LEDs wear and burn out just like light bulbs and it is recommended to replace all the LEDs with new instead of individual replacement. New strips are relatively inexpensive these days. If I can't find new strips or if they are too costly, I will do an individual replacement and turn down the backlight level. LEDs typically fail short circuit and in models with shutdown protection, the decreased sense voltage will trigger protection shut down on the LED controller.

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      #3
      Re: About replacing individual LEDS on BL strips

      Yes I've been purchasing them at between $10 and $20 each SET, so that's not bad, but to get that price I need to get them from Aliexpress and it has taken up to 3 months for the shipping some times here to Spain. That's why I would like to get my best with what I have at hand (used strips)

      Everytime I've replaced led strips I've asked the user to keep the BL level at LOW-MID to make sure it won't happen again. Also on LG's that have gone purple due to LED decay I've done the same

      But still I would like to know the conditions I need to check to replace individual LEDs and know what to check for compatibility, in case I ever take that route.

      Thanks!

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        #4
        Re: About replacing individual LEDS on BL strips

        You can check this thread to get an idea:
        https://www.badcaps.net/forum/showthread.php?t=92999

        Main differentiators are TV brand, size, shape, pads, voltage, color.

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          #5
          Re: About replacing individual LEDS on BL strips

          I have come across with 3V, 6V, and 9V leds. When I replace them, I will use a power supply to apply the required voltage and check the current it will draw. Then choose an led which draw the same or closest amount of current for the replacement. Of course, I will choose the one with the same or similar size.

          Please note, I did not studied electronics in college. It is just one of my hobbies. I would also like to know the correct way to do so.

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            #6
            Re: About replacing individual LEDS on BL strips

            Originally posted by tmhobadcap View Post
            I have come across with 3V, 6V, and 9V leds. When I replace them, I will use a power supply to apply the required voltage and check the current it will draw. Then choose an led which draw the same or closest amount of current for the replacement. Of course, I will choose the one with the same or similar size.

            Please note, I did not studied electronics in college. It is just one of my hobbies. I would also like to know the correct way to do so.
            Ok so you measure current flowing while applying right voltage, but how do you find out the right voltage before? Trying from 3V then 6V then 9V?

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              #7
              Re: About replacing individual LEDS on BL strips

              The power supply I use is with adjustable voltage and adjustable maximum current.

              When checking if the led is good or bad, I will start with 3V and limit the current to 20mA. If the led lights up and draws 20mA, then the led is 3V and is good. If the led does not light up but still draws 20mA, then the led is bad and is shorted. If the led does not light up and draws 0mA, then the led is either bad (open circuit) or not 3V. This can be confirmed by using higher voltage, like 6V and 9V or testing other leds from the same tv. If you do not have such power supply, you may need to add a resistor to limit the current.

              When finding the matched replacement led, then set the current to about 1 or 2 A.

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                #8
                Re: About replacing individual LEDS on BL strips

                Ok, at this time I don't have an adjustable PS at hand so I guess I will use other ways to provide incremental voltages to the LEDs and try
                Will see as soon as I got one to repair.

                Thanks!

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